In electrophotography, also known as xerography, electrophotographic imaging or electrostatographic imaging, the surface of an electrophotographic plate, drum, belt or the like (imaging member or photoreceptor) containing a photoconductive insulating layer on a conductive layer is first uniformly electrostatically charged. The imaging member is then exposed to a pattern of activating electromagnetic radiation, such as light. Charge generated by the photoactive pigment moves under the force of the applied field. The movement of the charge through the photoreceptor selectively dissipates the charge on the illuminated areas of the photoconductive insulating layer while leaving behind an electrostatic latent image. This electrostatic latent image may then be developed to form a visible image by depositing oppositely charged particles on the surface of the photoconductive insulating layer. The resulting visible image may then be transferred from the imaging member directly or indirectly (such as by a transfer or other member) to a print substrate, such as transparency or paper. The imaging process may be repeated many times with reusable imaging members.
An electrophotographic imaging member may take one of many different forms. For example, layered photoresponsive imaging members are known in the art. U.S. Pat. No. 4,265,990, which is incorporated herein by reference in its entirety, describes a layered photoreceptor having separate photogenerating and charge transport layers. The photogenerating layer is capable of photogenerating holes and injecting the photogenerated holes into the charge transport layer. Thus, in photoreceptors of this type, the photogenerating material generates electrons and holes when subjected to light.
More advanced photoconductive receptors contain highly specialized component layers. For example, a multilayered photoreceptor that can be employed in electrophotographic imaging systems can include one or more of a substrate, an undercoating layer, an optional hole or charge blocking layer, a charge generating layer (including photogenerating material in a binder, e.g., photoactive pigment) over the undercoating and/or blocking layer, and a charge transport layer (including charge transport material in a binder). Additional layers such as an overcoating layer or layers can also be included. See, for example, U.S. Pat. Nos. 5,891,594 and 5,709,974, which are incorporated herein by reference in their entirety.
The photogenerating layer utilized in multilayered photoreceptors can include, for example, inorganic photoconductive particles or organic photoconductive particles dispersed in a film forming polymeric binder. Inorganic or organic photoconductive material may be formed as a continuous, homogeneous photogenerating layer.
Upon exposure to light, the charge generated is moved through the photoreceptor. The charge movement is facilitated by the charge transport layer. The speed with which the charge is moved through the charge transport layer directly affects how fast the machine can operate. To achieve the desired increase in machine speed (ppm), the ability of the photoreceptor to move charge must also be increased. Thus, enhancement of charge transport across these layers provides better photoreceptor performance.
Conventional hole transport molecules, such as for example N,N′-diphenyl-N,N-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine, are generally incorporated into the charge transport layer to help mobility. However, as electrophotography advances, there is a growing need to further improve machine speed and devise ways to make different arylamine compounds that can be used to improve the hole mobility of existing photoreceptors. There has been historically very few synthesis reactions to produce variations in the arylamine structure. The Ullmann and Goldberg reactions have been generally used to produce triarylamines or diarylamines. These reactions, however, use large amounts (e.g., up to 10 mol equivalents) of solid, insoluble hydroxide or carbonate bases and thus are heterogeneous. The heterogeneity prevents these reactions from being conducted in a continuous mode to yield a higher and purer amount of product.
Recently, Buchwald chemistry has been used in place of the conventional Ullmann chemistry to produce arylamines not previously accessible. Buchwald chemistry has distinct benefits over the previously used methods in that the process cycle time is less, energy consumption is less and the crude product purity is higher, as disclosed generally in U.S. Patent Application Publication No. 2006/0111588 and U.S. patent application Ser. No. 10/992,690 to Bender et al., filed Mar. 6, 2003 , which are hereby incorporated by reference. Other more specific methods involving Buchwald Chemistry are disclosed in U.S. patent application Ser. No. 11/263,671 to Coggan et al., filed Nov. 1, 2005, and Ser. No. 11/274,506 to Coggan et al., filed Nov. 16, 2005, which are hereby incorporated by reference. Thus, Buchwald chemistry has been found to be more advantageous to use over the traditional methods and processes.
One issue that has been faced with using Buchwald chemistry, however, is that highly exothermic processes are involved in the production of the arylamine compounds. While these exothermic reactions do not present a problem when performed on a smaller scale, the reactions can present a safety risk when used in large-scale productions in batch mode due to the increase in reactant volume to heat transfer area ratio which makes heat management more difficult. A continuous mode production using Buchwald chemistry would avoid such safety risks and allow optimal conversion to product on a large-scale by increasing the heat transfer area available to the reacting volume. Unfortunately, Buchwald chemistry also produces a precipitate during the reaction, resulting in a heterogeneous mixture, which precludes performing Buchwald reactions in a continuous mode due to plugging/fouling of the reactor by the precipitate.
Thus, it is desirable to devise a new method in which continuous manufacture of arylamines can be performed using Buchwald reactions, even on a large-scale production.
The term “electrostatographic” is generally used interchangeably with the term “electrophotographic.” In addition, the terms “charge blocking layer” and “blocking layer” are generally used interchangeably with the terms “undercoat layer.” In addition, the term “arylhalide” is generally used interchangeably with the terms “haloaryl” and “haloaromatic.”